Process for prevention of decay of citrous fruits



Patented Nov. 1U, i925.

NWED r HARRY It. FULTU'N AND JOHN J. BUWMAN, OF WASHINGTON, DISTRICT OF COLUMBIA.

PRUGESS FUR PREVENTION OF DECAY 0F CITROUS FRUITS.

the Drawing.

Application filed September 11, 1925. Serial Ito. 55,861.

(GRANTED UNDER THE ACT 0F MARCH 3, 1883; 22 STAT. L. 625.)

To (ZZZ whom it my concern:

Be it known that we, HARRY R. FULTON and JOHN J. BOW AN, citizens of the United titates of America, and employees of the United States Department of Agriculture, residing at Washington, D. (1., whose postothce address is Department of Agriculture, Washington, D. U, have invented a new and useful Process for the Prevention of Decay of Citrous Fruits, of which the following is a specification.

This application is a continuation in part of the application for a patent by the same parties, which bears herial Number 42,552 and filing date July 9, 1925, entitled Process for the prevention of decay in fruits and vegetables.

This application is made under'the act of March 3, 1883, chapter 143 (*22 Stat. 625) and the invention herein described and claimed may be used by the Government of the United States, and its officers and employees, and by any person in the United States without the payment to us of any royalty thereon. W e hereby dedicate the same to the "free use of the Government and the people of the United States.

The object of this invention is to prevent the development of decay in citrous and other fruits and vegetables during the process of marketing, especially the prevention of the forms of decay of citrous fruits known as stem-end rot and blue-mold rot.

Stem-end rot of citrous fruits is caused b either of two fungi known as Phomopeie citri and Diplodia: petulant-is. The fruit apparently becomes contaminated or incipiently infected with these fungi while still on the trees, but actual decay does not set in until some days or weeks after the fruit has been removed from the trees in the process of marketing. Up to the present time control measures for these two stern-end rots have included one or more of the following procedures: (1) l leepin down sources of infection in the orchards y pruning out dead wood that harbors the two causal fungi; (2) spraying the young fruit with a suitable fungicide, such as Bordeaux mixture, so as to protect it against infection; (3) exposing the fruit after picking to certain gases, such as ethylene gas, or the fumes from imperfect combustion of gasolene or kerosene, under conditions of high humidity and temperature, in such way as to cause a loosening and shedding of the small portion' of stem, with the calyx and receptacle,

commonly called the button, which is usually left attached to the fruit proper in the ordinary methods of clipping the citrous fruit from the trees. end rot infectionseems to enter the fruit through, or in the immediate vicinity of this button, and its removal efi ectively prevents stem-end rot; (4c) refrigerating, pre

cooling, or otherwise keeping the temperature of the fruit low enough to retard and soprevent the development of stem-end rot during a reasonable marketing period. Blue-mold rot of citrous fruits is commonly caused by either of two fungi, known as Penicillium digital/um and Penicillin/m,

itwlicum. The methods now in general use perature of the fruit low enough to retard and so prevent the development of blue-mold rot during a reasonable marketing period.

The present invention controls or reduces liability to loss from stem-end rot by a'p lying to the fruit and leaving upon its s'ur ace a sufficient residue of certain chemicals that have an inhibiting or destroying effect on the fungi causing stem-end rot, as well as upon other fungi causing decay of citrous and other fruits, as well as other perishable vegetable products, such as blue-mold rot, anthracnose rot, blossom-end rot. These chemicals are especially suitable for the practical control of various decays because of (1) their antiseptic or inhibitory action on the fungi causing the rots; (2) their ability to go into solution in any surface moisture suflicient for causing germination of spores of any of these rot organisms;

(3) their ability to wet the surface, and adhere thereto and penetrate to some extent into the tissues of the fruits; (4:) their non- Most of the stem-' iii) tilt

injurious effect on the fruit itself; (5) their non-toxic properties for persons consuming the fruit.

The chemicals that We have found to be effective and useful for this purpose are alkaline carbonates, such as lithium carbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and ammonium carbonate.

The method of treatment consists essen tially in applying a solution of effective strength of any one of the chemicals in question, or a combination of them, to the fruit during the process of packing the fruit for marketing, and allowing a sufficient residue to remain on the surface of the fruit. The application may be made by means of a spraying device that will wet the fruit thoroughly with the solution after it has been washed in the usual way, or without being washed, and before it passes into the drying unit, the surplus spray drip being caught i311 a suitable tank or pan under the conveyor, and recirculated by means of a pump, or the fruit may be caused to dip in or be carried through a vat or tank in which the solution of effective strength is contained, the duration of the passage through such tank being sufiiciently long. to give effective results, usually from a fraction of a minute up to four or five minutes. Solutions of the chemicals named are effective at temperatures at which water is ordinarily used in citrus packing houses, namely, from about F; to about 85 F. and remain effective at higher temperatures up to the maximum that is safe for citrous fruit, namely up to about 120 F., and there is a gradual increase in effectiveness with increasing temperature. It is therefore advantageous to apply these solutions warm, at temperatures up to about 120? F., and in such case it would be advantageous to give rather long exposures, of about five minutes, in tanks specially equipped with steam pipes, hot water pipes, electric 1mmersion heaters, or pipes for circulating the chemical solution itself through coils in a suitable heater, or by other means for supplying and maintaining an; adequate supply 'ofheat. Any of the solutions may also be applied to the fruit as it passes over the scrnbbin brushes in the various types of washers in ordinary use, by simply keeping such brushes Wet with the solution.

The strength of solution for effective results also varies Within rather Wide limits for each chemical depending somewhat on the conditions of infection encountered by the fruit subsequent to treatment. Under.

.However, tests made in the development of this invention have shown each of the specified chemicals to be effective at somestrength within the rang indicated.

The specific advance over other methods previously used consists in leaving on fresh fruit or vegetables as prepared for market a surface residue of the above mentioned inhibiting chemicals that will effectively check the development of rot fungi over an extended marketing period.

We claim: a

A method for the prevention of decay of fresh citrous fruit-s consisting in the treatment of such fruits with an aqueous solution comprising lithium carbonate, at a temperature below 120 F.

' HARRY R. FULTON. JOHN J. BOWMAN. 

